My light box

[Carole]

Wasn't sure where to put this, but as it's a DIY jobbie I thought Skunkworks sort of fitted.

Up until now I have always used the dull daylight sky to do my flats and set to AV and 100ISO The Canon takes an appropriate length of sub, but now I have the Atik383L things are not so easy.  As those of you will know using a CCD camera you need to expose for a short length of time and measure the correct ADU (which I read in Maxim).  But the Atik383L has a further problem, a shutter, and if the image is too short you get a shadow from the shutter, so the trick is to take a longer sub and reduce the light source.

I decided that fiddling around every time to get the right length sub depending on how bright the sky was, was going to be a bit fiddly and that it would be better to have a known constant light source.  So I did the following:

Bought an EL panel from a company called Earlswell - these are cheaper than using the Gerd Neumann ones, and they are square with a slightly smaller square lit area.  They also put on a cable the length I requested, moved the invertor to the end furthest from the panel (so as to not make it top heavy) and also bought in a cigarette lighter plug at my request, so I was very impressed with their service.  I chose an A5 panel which is just the right size for my ED120 and ED80.

I also bought a sheet of Opal perspex off Ebay £6 and they cut that to size too.  This also renders the EL panel flat (which would otherwise be floppy) and also diffuses the light.
Being aware of light pollution at DSC I didn't want the corners of the lit square sticking out beyond the scope and dazzling every-one so decided to put all this inside an A5 cardboard box.  

cont....

[Carole]

The next thing was to find a way to fix the EL panel and opal perspex into the box so it wouldn't flop around, and also to keep it central as the A5 box is slightly bigger and the A5 panel is only just slightly larger than my ED120 aperture and so I needed to keep is positioned centrally.  When the EL panel arrived it was slightly larger than the size they gave so bigger than the Opal sheet, and the A5 box is slightly bigger still, so some of my ideas were not going to work.  In the end I did a Heath Robinson job and used blue tac, but it works fine.  Cut a small hole in the box to allow the cable to pass through.

I have two boxes the same and cut a 120mm hole in one and an 80mm hole in the other so I have two different lids for whichever scope I am using.

I did wonder whether I might need more than one layer of Opal perspex to dim the light, but so far on the narrowband filters I don't need to add any more, but have yet to try the LRGB filters which I have only just received.  (i.e. the sheet of perspex I ordered was large enough to cut into four pieces, so I have some left over).

This has cost me in total £48.  

Any way, enough waffle, the pictures (next post).

[Carole]

EL panel and perspex blue tac'd into the box and hole cut out for cable:


Close up where you can see the sizes didn't match:


Lid in place with hole for ED120:


In position on the scope (there is a slight light leak around the hole I cut out and I hope I can simply move up my dew heaters to oscure that:

[Mike]

A very neat solution Carole, although I think you will find that unless you are very careful the cardboard outer box will warp with the dew over time. I'd suggest looking for a plastic or wooden box you can put it in at some time in the future. Even one made from balsa and varnished would do the trick and would be easy to make.

[The Thing]

A very neat solution Carole, although I think you will find that unless you are very careful the cardboard outer box will warp with the dew over time. I'd suggest looking for a plastic or wooden box you can put it in at some time in the future. Even one made from balsa and varnished would do the trick and would be easy to make.

That's why I sandwiched my ELP between two sheets of picture mounting board with a circle cut out of one to go over the front of my OTA. Simple and water resistant. If you need to cut the light down get some dark translucent plastic from a folder cover from Smiths or Rymans and cover the ELP with it.

[Carole]

Yes, I did wonder about the cardboard maybe getting damp, but I have a couple of other cardboard things that I have made and provided I keep them inside a container when not being used they seem to have survived, but as you say I can always make a plastic or wooden one later if necessary.

Carole